The $6bn valuation was on a fully diluted basis, adding in all the options and warrants. On the same basis, the IPO values the company at up to $6.2bn. Although the share price is indeed lower — $11-$13 compared with $15.46 in the last private round — the diluted share count is now higher. There is not much of an embarrassing (or generous) discount at all.

http://www.ft.com/intl/cms/s/3/bd76d02a-85d2-11e5-9f8c-a8d619fa707c.html#axzz3qwhP3BSg